SE533853C2 - Drilling tools for chip separating machining and release stop for this - Google Patents

Abstract

In a first aspect, the invention relates to a drill of the loose top type, which is composed of a basic body (1) and a replaceable loose top (2). A jaw (20) is formed in the front end of the base body, which is delimited by two elastically flexible legs (21) and an intermediate axial support surface (22), and in which the loose top (2) can be pinched, more precisely by inner support surfaces (24) on the legs (21). ) resiliently applied to the side contact surfaces (26) of the top end. According to the invention, the two side contact surfaces (26) of the loose top extend backwards to the discharge surfaces (28), which are included in the upper end (9) of the loose top. By forming the diameter dimension between opposite side contact surfaces (26) ever closer to the front end of the loose top, the effect is obtained that the jaw legs (21) pinch the loose top in the area of the sine front ends, where the legs have their maximum bending ability. In this way, the legs provide a distinctive and reliable grip on the loose top. In a second aspect, the increase also refers to a loose stop as such. Publication image Fig.3

Description

40 45 50 55 60 533 853 this releasably connected and thus replaceable head, in which required cutting edges are included. In this way, most of the tool can be made of a comparatively inexpensive material with a moderate modulus of elasticity, such as steel, while a smaller part, namely the head, can be made of a harder and more expensive material, such as cemented carbide, ceramics, ceramics and the like. good chip separation ability, good machining precision and long service life. In other words, the head forms a wearing part, which can be discarded after wear, while the basic body can be reused several times (Lex. 10 to 20 bytes). A now accepted name for such cutting edge bearing heads is "loose tops", which will continue to be used in this document.

Loose-top type drilling tools are subject to a number of requirements, one of which is that torque can be transmitted in a reliable manner from the rotatable, driven base body to the loose-top. Furthermore, the base body must be able to easily absorb the rearward axial forces to which the loose top is subjected during drilling. Another requirement is that the loose top must be kept centered in a reliable manner relative to the basic body. A further requirement is that the loose top must be held to the base body not only during drilling of a hole, but also while pulling the drilling tool out of it. Another requirement or wish on the part of the users is that the loose top should be able to be mounted and dismantled in a fast and convenient way without the basic body necessarily having to be removed from the driving machine. In addition, the tool, and in particular the loose top made of expensive materials, must be able to be manufactured at low cost.

State of the art Both drilling tools and milling tools (pin millers) of the loose top type are richly described in the patent literature and can be divided into a number of different categories depending on the ideas on which the constructions are based.

A first category (see EP 1306152, EP 1328366, EP 1555075, WO03 / 031104, US 6695551, US 6783308, US 6899495, US 7114892, US 7134186 and US 2008/0193237) is based on the basic body of the tool at its front end being formed with a behind its axial support surface there is a slot which separates two legs, which due to the inherent elasticity of the material in the base body (usually steel) can be bent (e.g. by means of radial screws, eccentric keys, etc.), and in one way or another used to clamp loose top. For various reasons, however, attempts to manufacture such top-stop tools on an industrial scale have not been successful, partly due to the fact that the slot opens not only axially but also laterally and thus forms a trap, in which the separated metal chips can become entangled and cause difficulties, e.g. chip clogging.

The tools in a second category (see US 7 360974), which, like the tools in the first-mentioned category, use in the basic body, ib visible or elastically flexible legs for clamping the loose top, are based on the loose top being designed with a clamping pin projecting rearwardly from its axial contact surfaces , which is insertable into an existing hollow, between the limbs, and behind the required axial support surfaces, the clamping pin being partially coarser than the hollow so that the same, when inserted into the hollow, applies a resilient clamping force to the limbs desired position. However, even these loose-stopping tools are associated with difficult-to-master problems and disadvantages, which complicate industrial series production. A disadvantage is that the axial length of the loose top is noticeable in relation to the diameter; which means that the total volume of the loose top becomes comparatively large and causes expensive material consumption during production. Another disadvantage is that the nip or grip between the loose top and the legs is located to the rear parts of the legs (behind the required axial support surfaces), where the ability of the legs to bend out is minimal. The more the legs are tightened during clamping, the greater the risk that the front parts of the legs lose contact with the loose top. In extreme cases, it is even conceivable that gaps occur between the outside of the loose top and the inner support surfaces on the front parts of the legs. Another of your additional disadvantages (including complicated manufacturing) is that cooperating pairs of axial contact surfaces on the loose top and corresponding axial support surfaces on the base body are reasonably small and circumferentially located. In this way, the axial force transmission between the loose top and the base body can become unreliable, as well as imbalances can occur and jeopardize the centering of the loose top.

A loose stop tool, which differs markedly from the above tools, is described in EP 1013367. In this case, two flexible legs, which together with an intermediate axial support surface form the jaw in which the loose top is pinched, are designed as peripherally located finger-like material portions. projecting axially from a flat axial support surface. In this way, the latter does not have to be cut through by any slot or socket in which chips could get stuck. Due to the absence of any operatively necessary sperm pin projecting backwards from the axial contact surface of the loose top, the loose top can be made rather short in relation to the diameter; something that is material-saving and 95 100 105 110 115 120 533 853 cost-reducing. In addition, both the axial contact surface of the loose top and the axial support surface of the base body extend between ends which are located peripherally, i.e. the surfaces are given a length or a diameter dimension which is equal to the diameter of the drill.

However, a disadvantage of the drilling tool known from EP 1013367 is that the grip of the legs on the loose top risks becoming mediocre and unreliable. Thus, the legs are arranged to be rotated into pockets, which are recessed in the rear part of the two convex mantle surfaces, which form outer sides of the bars delimited by the chip channels in the loose top, each pocket having a limited axial extent, which in turn limits it. maximum possible length of the legs. In addition, the two (comic) inner support surfaces on the legs, which are clamped against the corresponding (conical) side contact surfaces on the loose top, are located approximately midway between the axial support surface of the jaw and the free ends of the legs. This means that the inner support surfaces of the leg clamps will pinch the loose top in a plane located comparatively close to its rear end. In other words, only the rear part of the loose top is kept clamped between the legs, while its front part - in which the cutting forces act most strongly - lacks effective clamping. Another negative consequence of the limbs having a limited length is that the tangential contact surfaces, which have the task of transmitting torque to cooperating surfaces in the corners of the loose top, have a limited area. In this way, the surface pressure can become annoyingly high and lead to deformation damage. Furthermore, there is an obvious risk that the loose top will be difficult to manufacture with such good precision that it can be centered in an accurate manner. Thus, it is practically impossible to precision grind the side contact surfaces existing in the interior of the pockets.

The present invention aims to obviate the above-mentioned disadvantages of the drilling tool known from EP 1013367 and to create an improved drilling tool. A primary object of the invention is therefore to create a drilling tool with a loose stop, which in its entirety is kept reliably clamped between the legs of a jaw in the basic body of the tool. In this case, the inherent elasticity of the leg clamps must be used in an appropriate manner to create an optimal grip on the loose top. Another purpose is to create a drilling tool, the loose top of which has a minimum length - and thus a minimum volume - in relation to its diameter; all with the aim of minimizing the consumption of expensive materials in connection with manufacturing. An additional purpose is to create a drilling tool whose basic body can transmit large torques to the loose top. Furthermore, the drilling tool must enable a quick, easy and convenient replacement of the loose top, without any aids other than a simple key and without the basic body necessarily having to be removed from the driving machine. An important factor in ensuring smooth changes is that the legs should offer only a moderate resistance to the tightening of the loose top in the jaw of the basic body, despite the ability of the legs to keep the loose top securely fastened. A further object is to create a drilling tool in which the loose top is centered - and maintains its centricity - in an accurate manner in relation to the base body.

According to the invention, at least the primary object is achieved by means of the features stated in the characterizing part of claim 1. Advantageous embodiments of the drilling tool according to the invention are further stated in the dependent claims 2-20.

In another aspect, the invention also relates to a loose stop as such. The distinctive features of this loose top are defined in the independent claim 21.

Advantageous embodiments of the loose top are further stated in the dependent claims 22-36.

Summary of the Invention The invention is based on the realization that the two limbs, which define a jaw in the basic body, have their greatest bending ability - and thus their optimal gripping ability - in the area of their free ends rather than near the rear ones. By placing the side contact surfaces of the loose top in the immediate vicinity of the front end of the loose top, this insight has been used to create a powerful grip or pinch along the front part of the loose top in connection with the cutting edges. For a given axial length of the loose top, the legs can be further given an optimized design, which in addition to improving the actual clamping effect also improves the legs' ability to transmit torque, in that the tangential contact surfaces of the legs can be made as long as the loose top. In addition, the location and design of the cooperating surfaces according to the invention offer a number of additional advantages, which are described later in this document.

Further elucidation of the prior art In the above-mentioned US 7360974 a drilling tool is presented, the loose top of which in itself comprises convex outer surfaces, which border on the front end of the loose top. In this case, however, the clamping of the loose top is taken care of by means of a rear clamping pin, which is insertable into a cavity located behind the axial support surfaces of the base body, which is delimited between two visible legs. This means that the clamping of the loose top takes place in an area where the legs, as previously pointed out, have a bending and gripping ability, which is significantly less than in their front parts.

Brief description of the accompanying drawings In the drawings are: Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. A cut perspective view showing the base body and loose top of the drilling tool in assembled condition, an exploded perspective view showing the loose top separated from the grurid body, an enlarged exploded view showing the loose top and the front end of the base body in bird's eye view, an exploded view showing the body and top of the frog perspective view, a cross section VI-VI through the base body in Fig. 4, a cross section VII-VH through the loose top in Fig. 4, a perspective view showing the loose top in a starting position in connection with turning in a jaw in the base body, a plan view from above of the loose top in the position according to Fig. 8, a side view of the loose top in the same position, a bird's eye view showing the loose top in the same position as in Fig. 8, although viewed at a different angle than in this, a detail section XII-XII in Fig. 11, an exploded view fire in side projection, a cross section XIV-XIV in Fig. 13, a cross section XV-XV in Fig. 13, 180 185 190 195 200 205 533 B53 Fig. 16 a schematic exploded view showing vital geometric features of the basic body resp. exaggerated scale in exaggerated scale, Fig. 17 a schematic plan view, which complements the image according to Fig. 16, Figs. 18-20 perspective exploded views showing an alternative embodiment of the invention, Fig. 21 a perspective exploded view showing a third alternative embodiment, and Fig. 22 an exploded view showing a further alternative embodiment of the invention.

Terminology In the following description and claims, a number of cooperating pairs of surfaces on the base body resp. the peak to be described. When these surfaces occur on the base body, the same are called "support surfaces", while the corresponding surfaces on the loose top are called "contact surfaces" (eg "axial support surface" or "axial contact surface"). It should further be pointed out that the loose top comprises a rear end in the form of a flat surface, which serves as an axial contact surface for abutment against an axial support surface in the base body. Depending on the context, this surface will be referred to as either the "rear end" or the "axial contact surface". In the drawings, the cooperating surfaces which are in contact with each other in the operative state of the drilling tool are shown with similar surface patterns.

Detailed description of a first embodiment of the invention The drilling tool shown in Figs. 1 and 2, which is made in accordance with the invention and has the shape of a so-called spiral drill, comprises partly a base body 1 and partly a loose top 2 in which the required cutting edges 3 are included. In its assembled, operative condition according to Fig. 1, the drilling tool is rotatable about a geometric center axis denoted by C, more precisely in the direction of rotation R. From Fig. 2 it appears that the basic body 1 includes front and rear ends 4, 5 between which a base body specific center axis Cl. In the rearward direction from the front end 4 extends a cylindrical shell surface 6, in which are recessed two chip channels 7, which in this case are helical (they could also be straight).

In the example, the chip channels 7 end in the vicinity of a collar included in a rear part 8, which is intended to be fastened to a driving machine (not shown). The loose top 2 also includes front and rear ends 9, 10 and a separate center axis C2 with which a jacket surface 11 is concentric. In this mantle surface 11 are recessed 210 215 220 225 230 235 533 853 two helical chip channels or chip channel sections 12 (see also Figs. 3-7), which form extensions of the chip channels 7 of the base body 1, when the loose top is mounted on the base body.

To the extent that the loose top 2 is centered correctly in relation to the base body 1, the individual center axes C1 and C2 coincide with the center axis C of the composite drilling tool.

Since most of the basic body 1 lacks interest in connection with the invention, in the future (Figs. 3-15) only its distal end portion will be illustrated together with the loose top 2, more precisely on an enlarged scale.

Reference is now made primarily to Figs. 3-7, which illustrate what is essential for the invention, and from which it appears that the chip channels 7 are delimited by concave surfaces 13, which extend between helical edges 14, 15. As can be seen from the section in Fig. 6 the concave limiting surfaces 13 of the two chip channels 7 delimit two barriers 16, between which there is a central core 17a from which the barriers protrude radially, more precisely in the plane P1 in which the base body 1 has the diameter D1. This core 17a is constituted by an inscribed circle between the adjacent parts of the concave surfaces 13 where the basic body is thinnest. The core 17a has a diameter designated D2. The peripheral, convex sub-surface of each such boom 16 is designated 6, since it forms part of the mantle surface of the base body. In an analogous manner, concave surfaces 18 (see Fig. 7) in the chip channels 12 of the loose top 2 delimit a pair of bars 19. The peripheral, convex surfaces of these bars are designated 11 because they form sub-surfaces in the outer surface of the loose top.

At the far end of the base body is formed a jaw 20 (see Figs. 3 and 4), which is delimited by two identical legs 21 and an intermediate bottom 22, which forms an axial support surface for the loose top. Each leg 21 comprises partly an inner support surface 24, which in this case is concave, and partly a tangential support surface 25, which faces forward in the direction of rotation R and has the task of transmitting torque from the leg to the loose top. In a manner known per se, the individual leg 21 is elastically flexible in order to be able to be resiliently clamped against the loose top 2. This is realized by the material in at least the front part of the base body 1 having a certain inherent elasticity (lower modulus of elasticity than the material in the loose top). preferably by being made of steel. The material in the loose top can in the traditional way consist of cemented carbide (hard carbide particles in binder metal), cermet, ceramic or the like. Advantageously, the bottom or axial support surface 22 of the jaw 20 is flat and extends at right angles to the center axis C1 and extends diametrically between the mantle surfaces 6 of the two booms. In other words, the axial support surface 22 has a diametrical longitudinal extent which is equal to the diameter D1 of the basic body.

As can be seen from Fig. 5, the rear end 10 of the loose top 2 is represented by an axial contact surface which, like the axial support surface 22, is most suitably flat and extends at right angles to a center axis C2. The axial contact surface 10 also extends between diametrically opposite circumferential surfaces, namely the surfaces 11. Furthermore, the loose top 2 comprises external side contact surfaces 26, which in the example are convex, and against which the inner support surfaces 24 of the legs can be clamped.

The front end 9 of the loose end (see Fig. 3), in which the cutting edges 3 are included, is represented by a surface (end surface), which is composed of a plurality of sub-surfaces, which in this case are in pairs identical and which are therefore not described separately. After the individual cutting edge 3 (viewed in the direction of rotation) a primary clearance surface 27 is formed, which has a moderate clearance angle and merges into a secondary clearance surface 28 with a larger clearance angle, more precisely via a boundary line 29. Via a further boundary line 30 the secondary clearance surface 28 passes in a third clearance surface 31, which in turn merges into a rear chip channel 12 via an arcuate boundary line 32. The concave surface 18 of the chip channel 12 extends at least partially up to a cutting edge 3 and forms a chip surface therefor. Of course, the composite end surface 9 can also include other sub-surfaces than those exactly exemplified in the drawings. In connection with the casing surface 11, a guide strip 33 is formed, which includes a clearance surface and has the task of guiding the drilling tool, but also surface leveling the hollow wall generated axially behind the cutting edges. The diameter of the drilled hole is determined by the diametrical distance between the peripheral points 3a, 3b where the cutting edges 3 meet the guide strips 33. It should also be pointed out that the two cutting edges converge in a tip T, which forms the foremost part of the loose top, and which may be included. a so-called chisel egg and a minimal centering stud (no designations).

As far as the drilling tool shown so far has been described, the same is essentially previously known from the above-mentioned EP 1013367.

A feature characteristic of the invention is that the two convex side contact surfaces 26 of the loose top (see Figs. 3 and S) extend axially backwards from the front end 9 of the loose top, more specifically in order to make it possible to establish the nips or grips of the legs as far as possible along the loose top. The side contact surfaces 26 are formed on two diametrically opposite, slightly C-shaped web portions 26a (see Fig. 7), which consist of material portions which are thickened relative to a core 17b included in the loose top, which in this case it has substantially the same diameter D2 as the core 17a of the base body 1. A diametrical dimension generally denoted by DM between the side contact surfaces 26 is therefore considerably larger than the diameter D2 of the core 17b, which is of course determined by the smallest distance between the concave boundary surfaces 18 of the two chip channels.

As can be seen from Figs. 3 and 5, the individual side contact surface 26 is delimited by front and rear boundary lines 35, 36 and a pair of side boundary lines 37, 38. The front, broken boundary line 35 forms a transition towards the two clearance surfaces 28 of the front end 9, 31, while the rear boundary line 36 is located near the rear axial contact surface 10 of the loose top and separated therefrom only via a narrow radius transition 39. The side boundary line 37 forms a transition towards the concave boundary surface 18 of the chip channel 12 and in this case the chip channel is helical the side boundary line 37 therefore to run at a moderate, acute angle (no designation) in relation to the center axis C2 of the loose top. The side boundary line 37 extends between front and rear end points 40, 41, of which the rear 41 drags the front 40 during rotation, and of which the front 40 is located at a greater radial distance from the center axis C2 than the rear 41 (0.03 etc. according to the concrete example below). The opposite side boundary line 38 forms a transition towards a niche surface 42. As best seen in Fig. 7, this niche surface 42 merges into a tangential contact surface 43 in the immediate vicinity of the mantle surface 11. In the operative state, the tangential support surfaces 25 of the legs 21 are held against the surfaces 43 to transmit torque to the loose top, while the inner support surfaces 24 of the legs are held against the lateral contact surfaces 26 following the tangential contact surfaces rotationally to clamp the loose top.

As can be seen from Figs. 3-5, different sub-surfaces, which together are included in the front end surface or end generally denoted by 9, are located at different levels and at different angles in relation to each other. Of these sub-surfaces, the two sub-surfaces 28, 31, which form clearance surfaces behind the individual cutting edge 3, and to which the side contact surfaces 26 are connected, are partly wedge-shaped and taper in the direction of the front tip T.

A further, vital feature, which is not visible to the naked eye in Figs. 1-7, has been shown schematically on an exaggerated scale in Figs. 16 and 17. In these figures, the visible limbs 21 are thought to be unloaded or de-energized. The inner support surfaces 24 of the leg members 21 are in this case cylindrical and concentric with center axes C3, and have a radius of curvature which is 300 305 310 315 320 325 330 533 B53 11 denoted r 1. These center axes C3 are in the example parallel to the center axis C1 of the base body, i.e. surfaces 24 run parallel to Cl. The side contact surfaces 26 on the loose top 2 are also cylindrical and concentric with center axes C4, and have a radius of curvature r2. In this case, however, the center axes C4 diverge in the direction from the rear end 10 of the loose top towards the front 9, more specifically in a divergence angle a. In Fig. 16, RPa denotes a reference plane extending at right angles to the center axis C2 of the loose top the distance L1 from the rear end 10 of the loose top 10. In the example, RPa is intended to be inserted in level with the front end boundary lines 35 of the side contact surfaces 26, i.e. the transitions to the release surfaces 28 at the distal end 9 of the loose top. A reference plane RPb through the base body 1 is located at the level of the free ends 51 of the leg clamps, more precisely at the axial distance L2 from the axial support surface 22.

Two other reference planes RPc and RPd (the former of which are located at the level of the rear end boundary lines 36 of the side contact surfaces 26) are comparable in that they are located at one and the same axial distance L3 from the axial contact surface 10 and the axial support surface 22, respectively. not to be confused with the term "diameter") between the inner support surfaces 24 of the limbs. Furthermore, DM2 denotes a diametrical dimension between the side contact surfaces 26 in the plane RPc, and DM3 a corresponding dimension in the plane RPa. As the side contact surfaces 26 run apart at the divergence angle u, DM3 becomes larger than DM2. This means that said diameter measurement gradually increases from a minimum value DM2 in the plane RPc to a largest value DM3 in the plane RPa. Expressed in an armed manner, the largest diametrical dimension in any reference plane along the center axis C2 becomes larger the closer to the front end 9 the reference plane is located.

In a concrete embodiment of the drilling tool according to the invention, DM2 amounts to 9.00 mm, while DM3 amounts to 9.08 mm. This means that ot amounts to 0.56 ° (a / 2 = 0.28). In itself, DMI could be exactly as large as DM2. In order to facilitate installation of the loose top and avoid tolerance problems, however, a certain excess of DMI is preferred, which is therefore, under the said conditions, advantageously set at 9.02 mm. When the loose top is mounted in the jaw - which is done by turning and not by axial pressing - each leg will therefore be bent out 0.08 / 2-0.02 / 2 = 0.03 mm in the area of its front, free end. In other words, the nip or grip of the side members 21 is concentrated to the reference plane RPb located at the level of the free ends of the side members 51 335 340 345 350 355 360 533 B53 12, where the legs have their maximum bending ability. During the rotation, the legs 21 will join the diverging shape of the loose top along a large part of its longitudinal extension L2 in the rearward direction from the front end 9.

Fig. 17 shows the inner support surfaces 24 with a radius of curvature r1_ which is less than half of the DMI (r1 <DMI / Z), the center axes C3 being located eccentrically with respect to the center axis C1 of the base body. Within the scope of the invention, C1 and C3 can also coincide, the two surfaces 24 forming parts of a common cylinder or circle.

Furthermore, the side contact surfaces 26 of the loose top in this case have a radius of curvature r2_ which is smaller than r1, which means that the surfaces 26, 24 obtain simple line contact in the operative state. The radii of curvature of the surfaces are also 26; can vary and be either as large as r; (coincident surface contact) or larger, whereby double line contact is obtained.

Reference is now made to Fig. 5, from which it appears that the axial support surface 10 of the loose top obtains a §-like contour shape, e.g. due to the presence of the C-shaped body portions 26a (see Fig. 7), which thicken the loose top relative to the central core 17b. Fig. 3 shows that the axial support surface 22 in the base body 1 has the same §-like contour shape as the axial contact surface 10 on the loose top 2. This shape has been made possible by the width or tangential extension of the leg 21 between the surface 25 and an opposite surface 44 (not seen on the left the leg in Fig. 4, but well on the right), is reduced in relation to the corresponding width of the mantle surface 6. In this way, a space existing in rotation in front of each leg 21 can be used to create an ax blade-like peripheral surface portion, the shape of which corresponds to the corresponding peripheral surface portion of the surface 10. Av F ig. 5 further shows that the axial contact surface 10 extends diametrically between arcuate boundary lines 11a in connection with the mantle surface 11. In an analogous manner the axial support surface 22 (see Fig. 3) extends between arcuate boundary lines 6a towards the mantle surface 6 of the base body.

Referring to Figs. 3 and 4, it should be noted that the individual leg 21 includes two types of radius transitions, namely a first, upright radius transition 45 between the inner support surface 24 and the tangential support surface 25, and a second, horizontal radius transition 46 between the axial support surface 22 and the surfaces 24, 25. The radius transition 46 (which is concave) has a smaller radius than a corresponding radius transition 39 on the loose top. The upright radius transition 45 (which is convex) has a larger radius than the niche surface 42 (see Figs. 3 and 7).

Normally, the resilient nip between the legs 21 of the base body should be sufficient to retain the loose top in the jaw even when pulling the drilling tool out of a hole, 365 370 375 380 385 390 533 B53 13 when the loose top is subjected to forces which seek to tear it out of the jaw. In order to avoid unintentional pulling out of the loose top, the basic body has been provided with special locking means, which in the embodiment according to Figs. 1-15 consist of brackets or lips 47, which protrude from the front ends 51. protruding radially inwardly from the associated leg, the same in the preferred embodiment is formed adjacent to the torque transmitting tangential support surface 25 for bridging a sub-surface 48 (see Fig. 3) included in the front end 9 of the loose top. This sub-surface 48 is circumferentially located and inclined obliquely downwards / backwards (in the direction of rotation) towards the tangential contact surface 43 of the loose top. The lip 47 is wedge-shaped and includes an inclined lower stop surface 49 (see Figs. 4 and 5), which faces the partial surface 48. drilling, in that the lip 47 is located at a certain distance from the surface 48 in the operative state. This is clearest from the detail section in Fig. 12, which shows how the stop surface 49 of the lip is spaced a short distance from the sub-surface 48. Only if the elastic legs would release the resilient frictional grip in difficult circumstances if the loose stop does the lips 47 come into operation. In other words, the lips are passive under normal circumstances and are activated only when needed. In this context, it should be pointed out that the drilling tool is still rotated during extraction, so that the surface 25 is always kept strongly pressed against the surface 43 on the loose top. The lips 47 therefore form a foolproof locking means during the extraction of the drilling tool.

In Figs. 6 and 12, 50 denotes two coolant channels running through the base body 1, which open into the front end surfaces 51 of the pouring clamps 21 (see also Fig. 3).

In Figs. 8-11, the loose top 2 is shown in a starting position immediately before the rotation in the jaw 20 of the basic body. In order for the loose top to temporarily maintain a reasonably centered position in relation to the basic body during the subsequent rotation of the jaw, the basic body and the loose top are designed with cooperating coarse centering means. In the embodiment according to Figs. 1-15, these means consist partly of a cylinder pin 52 (see Figs. 4 and 5), which projects axially rearwardly from the axial contact surface 10 of the loose top 2 and is concentric with the center axis C2, and partly of a hole 53 (see Figs. 3), which opens into the axial support surface 22 of the base body and is concentric with the center axis C1. The pin 52 has a diameter which is smaller than the inner diameter of the hole 53, in that the pin only has the task of retaining the loose top in a reasonably centered position during the turning. In other words, neither the pin 395 400 405 410 415 420 533 B53 14 nor the hole are operatively active during drilling, as they lack surface contact with each other. The pin and the hole can therefore be created without any requirement for dimensional accuracy.

Fig. 3 shows how the release top 2 comprises a key grip in the form of two grooves or seats 55, which are located circumferentially and open partly in the mantle surface 11 and partly in the further end 9 (in connection with the primary release surface 27). Due to the peripheral location of the seats 55, the distance between them becomes optimal, so that a suitably designed key (not shown) can apply a strong torque to the loose top without excessive manual force in connection with the turning.

Reference is now made to Figs. 13-15, of which Fig. 13 constitutes an exploded view in side projection and Figs. 14 and 15 cross-sections through the loose top and the base body, respectively. From the cross section in Fig. 14 it can be seen that the tangential contact surface 43 of the loose top forms an acute angle ß with an imaginary radius tangential to the niche surface 42. Fig. 15 shows that the tangential support surface 25 on the individual leg 21 forms an angle y with an imaginary radius tangential the radius transition 45 between the surface 25 and the inner support surface 24. When these surfaces 25, 43 are applied to each other during drilling, the loose top will apply to the individual leg 21 a force component which strives to press the leg against the core of the loose top. In other words, the inclination of the surfaces 25, 43 helps to keep the inner support surfaces 24 of the legs distinctly pressed against the side contact surfaces 26 in addition to the clamping force which the inherent elasticity of the legs guarantees. The angles ß and y can in themselves be equal, e.g. in the range 20-30 °.

However, they can also differ, for example by making y slightly larger than ß. In this way, the torque transmission is concentrated on the inner parts of the tangential contact surfaces 43 in connection with the niche surfaces 42.

By precision grinding or otherwise machining at least the pairs of side contact surfaces 26 and tangential contact surfaces 43 to meticulous dimensional accuracy, the loose top obtains a good centering and positioning precision. The fact that the tangential contact surfaces 43 are also finely machined contributes to this to a great extent, because in this way it is ensured that the legs 21 are applied simultaneously - and without play - against them. The axial contact surface 10 can also be precision ground.

The function and advantages of the drilling tool according to the invention 425 430 435 440 445 450 533 853 When the loose top 2 is to be applied to the base body 1, it is inserted axially into the jaw 20 between the legs 21 to the initial position shown in Figs. 8-11. Here, the pin 52 engages the hole 53 and holds the loose top temporarily in place in a central position. From this starting position, the loose top is rotated in a direction of rotation V, which is opposite to the direction of rotation R of the basic body, until the surfaces 25, 43 make contact. together. When the side contact surfaces 26 of the loose top initially approach the inner support surfaces 24 of the legs 21, a lower part of the side boundary line 37 (at a certain axial distance from the lower end point 41, depending on the difference between DMI and DM2 according to Fig. 16) will first contact the inner support surface. the remainder of the side boundary line 37 is separated from the inner support surface via a gap G (see Fig. 10), which widens forwards (upwards in the figure). During the continued rotation from this position, gradually larger parts of the side boundary line 37 will come into contact with the inner support surface and then reach an end position where it - under ideal conditions - has contact with the inner support surface along most of its length. In this end position, the tangential support surface 25 of the leg is held against the cooperating tangential contact surface 43 on the loose top. During the rotation, the legs 21 will successively apply a growing clamping force 26 to the side contact surfaces 26 of the loose top, which finally reaches a maximum value. An advantage of the boundary line 37 of the individual side contact surface 26 being inclined relative to the center axis of the loose top - and not running parallel thereto - is that the loose top can initially be rotated with a moderate resistance, which gradually increases until the loose top assumes its operative end position. In practice, this means that the loose top can be turned in a smooth manner without having to apply excessively large manual forces to the key in question. When the loose top is to be released, the direction of rotation V is reversed, after which the loose top is pulled out axially from the jaw of the basic body.

A basic advantage of the tool according to the invention is that the loose top is in any case pinched between the front parts of the two side contact surfaces, where the legs are most flexible and provide optimum clamping force. To the extent that the side contact surfaces - as in the example shown - extend all the way to the rear axial contact surface, the loose top is pinched along most of its length (if DMI and DM2 are made equal in size, a pinch along the entire length would be possible). In this way an extremely good grip is ensured, and the loose top can be given a minimal volume in relation to its diameter. Thus, in the example shown, the loose top has an axial length which is considerably smaller than its diameter. More specifically, the total length (from the axial contact surface 10 to the tip T) amounts to only approx. 60% of the diameter.

The advantageous consequence of this relationship is that the consumption of expensive material in the redemption peak is reduced to an absolute minimum. Another advantage is that the basic body can transmit considerable torques to the loose top in that the tangential support surfaces of the legs can be given an optimized length. Furthermore, the loose top can be mounted and dismounted in a simple and convenient way without other aids than a simple key. The fact that the side contact surfaces of the loose top are delimited by oblique side boundary lines, which are successively brought into contact with the inner support surfaces of the leg clamps, also contributes to the smooth mounting.

In addition, the centering of the loose top relative to the base body can be ensured in a simple manner in connection with industrial series production. Thus, not only the two side contact surfaces on the loose top but also the axial contact surface and the two torque-absorbing tangential contact surfaces are well exposed and easily accessible for a grinding tool with the aid of which these surfaces can be precision ground. In other words, the surfaces are not delimited by any protruding limiting surfaces of the type included in the pockets in the loose top according to EP 1013367.

Summary of Alternative Embodiments of the Invention In Figs. 18-20 show an alternative embodiment, in which the side contact surface 26 of the loose top has been shortened and ends at a certain distance from the rear end 10. More specifically, the side contact surface 26 merges into a waist 56, which is delimited by a pair of opposite, convex surfaces 56a. The transition between the surfaces 26 and 56a may advantageously be conical surfaces 57. The individual surface 56a cooperates with a cylindrical or otherwise rotationally symmetrically shaped surface 58a on a rim 58 in the area between the inner support surface 26 and the axial support surface 22 of the jaw to form a coarse centering means. , which replaces the combination of pin and hole in the previously described embodiment. The surfaces 56a may have a diameter which is smaller than the diameter of the surfaces 58a, whereby the surfaces do not come into contact with each other in the operative state.

In contrast, the cooperating pairs of surfaces 56a, 58a act as a means for holding the loose top in a center position in connection with the rotation. The fact that the side contact surfaces 26 are shortened also has the advantage that the risk of tolerance errors in the rear part of the loose top is eliminated, whereby the pinching of the loose top is concentrated to the front part of the loose top, as determined by the longitudinal extent of the surfaces 26.

Fig. 21 shows a further coarse centering means in the form of a pin 59, which protrudes from the axial support surface 22 of the base body and is coneentric with the center axis C1.

This pin cooperates with a central hole 60, which grooves in the axial contact surface 10 of the loose top. Similar to the embodiment according to Figs. 1-15, the diameter of the hole 60 is larger than the diameter of the pin 59, 485 490 495 500 505 510 515 533 or the pin requires some fine dimensional accuracy. The only task of the pin and the hole is to temporarily coarsely center the loose top in connection with the start of its tightening.

Fig. 22 illustrates an additional alternative drilling tool, which includes a different type of axially reading locking means than those shown in Figs. 1-15. In this case the locking means consist partly of a seat 61 taken out at the rear end of the individual leg 21, and partly of a male member 62 located near the axial contact surface 10 of the loose top 2, which is insertable into the seat when the loose top is turned into its final clamp between the legs. operational end position. In the preferred embodiment, the seat 61 is in the form of a strap located behind the individual tangential support surface 25 of the leg 21, more specifically between the rear end of this surface and the axial support surface 22 of the jaw 20, a concave clearance surface 63 forming a transition between the chute and the axial support surface. The male member 62 is constituted by a ridge formed between the axial contact surface 10 and the rear end of the tangential contact surface 43 of the loose tip. the loose top is strong enough to retain it in the jaw 20. In other words, the locking means - like the lips 47 in the previously described embodiment - are normally passive and are activated only if and when the legs inadvertently tend to lose their grip on the loose top.

Conceivable modifications of the invention Within the scope of the invention, as defined in the following independent patent claims, various modifications can be made. Thus, the side contact surfaces of the loose top can be given both varying length and varying shape, provided that they extend axially backwards from the front end of the loose top. Correspondingly, the legs defining the front jaw in the base body can be designed in different ways provided that the inner support surfaces can cooperate with the side contact surfaces of the loose top in the previously described manner. The required difference in diametrical dimensions between the side contact surfaces of the loose top and the inner support surfaces of the leg clearance can also be realized in other ways than with just cylindrical surfaces, e.g. conical surfaces or a combination of cylindrical and conical surfaces. Instead of being convex and concave, respectively, the side contact surfaces and the inner support surfaces can also be flat.

Furthermore, it is conceivable to apply the invention to drilling tools, the loose ends of which comprise three cutting edges, three chip channels and three side contact surfaces, which co-operate with three visible legs. In addition, it should be pointed out that the rear axial contact surface of the loose top does not necessarily have to consist of a single, flat surface. Thus, the surface may consist of two or fls separated parts located in a common plane.

Claims (36)

520 525 530 535 540 545 550 533 853 19 PATENT REQUIREMENTS Drilling tool for chip removal processing, comprising on the one hand a base body (1) with front and rear ends (4, 5) and a jacket surface (6), which includes two countersunk chip channels (7), and is concentric with a geometric center axis (C1) around which the base body is rotatable in a given direction of rotation (R), and includes two recessed chip channels (7), and a loose stop (2), which includes front and rear ends (9, 10), of which the rear (10) serves as an axial contact surface, and a mantle surface (11) concentric with a geometric center axis (C2), which comprises two recessed chip channels (12) between which two barriers (19) radially projecting from a central core (17b) are delimited, which at the front end include each cutting edge (3) and a number rotationally according to this existing clearing surface (27, 28, 31), the front end (4) of the base body (1) comprising a jaw (20), which is delimited by a bottom (22) and two from this axially projecting, circumferentially located leg ares (21), which are elastically flexible and have the task of clamping the loose top (2) in the jaw (20), more precisely by a pair of inner support surfaces (24) on the legs (21) resiliently pressed against a pair of outer side contact surfaces (26). ) on the loose top (2), as a result of a larger diametrical dimension between the side contact surfaces being larger than an analogous diametrical dimension between the inner support surfaces, when the legs are loaded, the loose top being rotatable in and out of engagement with the jaw (20) in the base body, characterized therefrom, that both side contact surfaces (26) of the loose top (2) extend rearwardly from at least one clearing surface (28) included in the front end (9), and that a largest diametrical dimension (DM3) between the side contact surfaces (26) in a center axis (C2) of the loose top perpendicular reference plane (RPa), located closer to the front end (9) than the rear (10), is greater than an analogous diameter dimension (DM1) between the inner support surfaces (24) of the legs (21) when these are unloaded. Drilling tool according to claim 1, characterized in that a larger diametrical dimension (DM3) in arbitrary reference planes, which extends at right angles to the center axis (C2) of the loose top, is larger the closer the front end (9) of the reference plane is located. Drilling tool according to Claim 1 or 2, characterized in that the inner support surfaces (24) of the legs (21) are concave and the lateral contact surfaces (26) of the loose top (2) are convex. Drilling tool according to claim 3, characterized in that the inner support surfaces of the two leg clamps (21) consist of first cylinder surfaces (24), which are concentric with geometric center axes (CS), which run parallel to the center axis (C1) of the base body (1), when 555 560 565 570 575 533 853 the legs (21) are unloaded, and that both side contact surfaces of the loose top (2) are constituted by other cylinder surfaces (26), which are concentric with geometric center axes (C4), which diverge in direction from the rear end of the loose top ( 10) towards the front (9), the reference plane (RPa) in which the diametrical dimension (DM3) is largest, being located at the level of the front ends (35) of the other cylinder surfaces (26). Drilling tool according to one of Claims 2 to 4, characterized in that the largest diametrical dimension (DM2) in a reference plane (RPc) closest to the rear end (10) of the loose top (2) is at most equal to the largest diametrical dimension (DM1) between the inner support surfaces. (24) on the legs (21) in a comparable reference plane (RPd) therethrough. Drilling tool according to Claim 4 or 5, characterized in that the individual first cylinder surface (24) has a radius of curvature (r1) which differs from the radius of curvature (rg) of the cooperating second cylinder surface (26). Drilling tool according to one of the preceding claims, characterized in that the axial support surface (22) of the base body (1) has substantially the same shape and size as the axial contact surface (10) of the loose top (2). Drilling tool according to one of the preceding claims, characterized in that the individual side contact surface (26) on the loose top (2) is connected to a chip channel (7) which is helical, so that the side contact surface comprises a side boundary line (37) which runs in a acute angle relative to the center axis (C2) of the loose top (2) viewed in side projection. Drilling tool according to one of the preceding claims, characterized in that the individual side contact surface (26) on the loose top (2) extends between front and rear end boundary lines (35, 36), the front (35) of which forms a direct transition towards said release surface (28) in the front end (9) of the loose top, while the rear (36) is located closer to the rear end (10) of the loose top than the front (9). Drilling tool according to one of the preceding claims, characterized in that both side contact surfaces (26) of the loose top (2) extend axially all the way from the clearance surface (28) of the front end (9) to a radius transition (39) towards the axial contact surface (10). Drilling tool according to one of Claims 1 to 9, characterized in that the two side contact surfaces (26) of the loose top (2) extend axially rearwardly from the clearance surface of the front end (9) 580 585 S90 595 600 605 533 853 21 (28) to a rear waist (56), which is delimited by two opposite, convex sub-surfaces, which are located closer to the center axis (C2) than the side contact surfaces (26). Drilling tool according to one of the preceding claims, characterized in that it comprises centering means (52, 53; 56, 58; 59, 60) for temporary rough centering of the loose top (2) in connection with its rotation in the jaw (20) of the base body (1). ). Drilling tool according to claim 12, characterized in that the centering means consist of a centrally located pin (52) projecting axially rearwardly from the axial contact surface (10) of the loose top (2) and a centrally located hole (53) having a larger diameter than the pin (52) and opens into the axial support surface (22) of the base body. Drilling tool according to claim 12, characterized in that the centering means comprise on the one hand a centrally located hole (60) which opens into the axial contact surface (10) of the loose top (2), and on the other hand a centrally located pin (59) having a smaller diameter than the hole and protrudes from the axial support surface (22) of the base body (1). Drilling tool according to claims 11 and 12, characterized in that the centering means consist of the two convex sub-surfaces on the waist of the loose top (56) and a pair of edges (58) formed in connection with the rear ends of the legs (21) with concave, internal guide surfaces. . Drilling tool according to one of the preceding claims, characterized in that the base body (1) comprises locking means (47, 48; 61, 62) for preventing unintentional axial extension of the loose top (2) from the jaw (20). Drilling tool according to Claim 16, characterized in that the locking means consists of a bracket (47) formed on the free end of the individual leg (21). Drilling tool according to claim 17, characterized in that the bracket (47) is located in axial extension of a torque-transmitting tangential support surface (25) on the leg (21), and spaced from a partial surface (9) included in the front end (9) of the loose end (2). 48). Drilling tool according to claim 16, characterized in that the locking means comprises partly a seat (61) recessed in the rear end of the individual leg (21) and partly a male member (62) located in connection with the axial contact surface (10) of the loose top (2), which is insertable in the seat. 610 615 620 625 630 635 533 B53 22 Drilling tool according to claim 19, characterized in that the seat consists of a groove (61) located behind the tangential support surface (25) of the leg, and the male member of a ridge (62) located behind a cooperating tangential contact surface (43) on the loose top (2). Loose stop for drilling tools, comprising front and rear ends (9, 10), and a mantle surface (11) concentric with a geometric center axis (C2), in which are recessed at least two chip channels (12), between which two are delimited from a central core (17b) radially projecting booms (19), which in the front end (9) each comprise their cutting edge (3) and a number of rotational surfaces (27, 28, 31) existing after this, and two external side contact surfaces (26) with task of widening a loosely receiving jaw between two legs of a cooperating base body, the rear end being constituted by an axial contact surface (10), which forms a right angle with the center axis (C2) and extends between diametrically opposite boundary lines (1a) adjacent to the jacket surface (11), characterized in that the two side contact surfaces (26) extend rearwardly from at least one clearance surface (28) included in the front end (9). Loose stop according to claim 21, characterized in that a larger diametrical dimension (DM) between the side contact surfaces (26) in arbitrary reference planes (RP), which extends at right angles to the center axis (C2), is larger the closer to the front end (9). ) the same are located. Loose stop according to Claim 22, characterized in that the side contact surfaces consist of cylindrical surfaces (26) which are concentric with geometric center axes (C4) which diverge in the direction from the rear end (10) towards the front (9). Loose stop according to one of Claims 21 to 23, characterized in that the side contact surfaces (26) are included in body portions (34) which are thickened relative to the core (17b). Loose stop according to one of Claims 21 to 24, characterized in that the individual side contact surface (26) is connected to a chip channel (12) which is helical, the side contact surface having a side boundary line (37) which runs at an acute angle relative to the center axis. (C2) viewed in side projection. Loose stop according to one of Claims 21 to 25, characterized in that the individual side contact surface (26) extends between front and rear end boundary lines (35, 36) of which the front (35) forms a direct transition to said release surface (28) in the front end (9), while the rear (36) is located closer to the rear end (10) of the loose top than the front (9). Loose stop according to claim 26, characterized in that the two side contact surfaces (26) extend axially all the way from the clearance surface (28) of the front end (9) to a radius transition (39) adjacent to the axial contact surface (10). Loose stop according to claim 26, characterized in that the two side contact surfaces (26) extend axially from the clearance surface (28) of the front end (9) to a rear waist (56) with reduced cross-sectional area. Loose stop according to one of Claims 21 to 28, characterized! in that it comprises centering means for temporary coarse centering in connection with its rotation in the jaw of a cooperating basic body. Loose stop according to Claim 29, characterized in that the coarse centering means consists of a centrally located pin (52) which projects axially rearwardly from the axial contact surface (10). Loose stop according to Claim 29, characterized in that the coarse centering means consists of a centrally located hole (60) which opens into the axial contact surface (10). Loose stop according to claims 28 and 29, characterized in that the waist (56) comprises two convex guide surfaces (56a), which serve as coarse centering means. Loose stop according to one of Claims 21 to 32, characterized in that it comprises a projecting male member (62) located in connection with the rear axial contact surface (10) with the task of locking the loose top axially. Loose stop according to claim 33, characterized in that the male member (62) is located between the axial contact surface (10) and a torque-absorbing tangential contact surface (43) on the individual boom (19). Loose stop according to Claim 34, characterized in that the male member consists of a ridge (62). Loose stop according to one of Claims 21 to 35, characterized in that it comprises a key grip in the form of a pair of grooves (55) which are recessed in the periphery of the front end (9).